Summary IGCSE Chemistry Notes Latest 2023 / 2024

IGCSE Chemistry Notes for All Chapters B1. States of Matte r L.1. States of matte r Differences in the properties of the three states of matte r. Changes of physical states and the effect of increasing temperature at atmospheric pressure. 1 Evaporation → a process occurring at the surface of a liquid, involving the change of state from a liquid into a vapour at a temperature below the boiling point. Water is quite a volatile liquid. Ethanol, with a boiling point of 78 °C, is more volatile than wate r. It has a higher volatility than water and evaporates more easily. It is possible, at normal temperatures, to condense a gas into a liquid by increasing the pressure without cooling. If the surrounding pressure falls, the boiling point falls. If the surrounding pressure is increased, the boiling point rises. A pure substances consists of only one substance without any contaminating impurities. A pure substance melts and boils at definite temperatures. This means that we can use BP to test the purity of a sample. These values can also be used to check the identity of an unknown substance. Impure substances boil over a range of temperatures. BP increase & MP decrease. A cooling Curve show that heat energy is needed to change a solid into a liquid, or a liquid into a gas. When state change from gas to liquid or liquid to solid, heat energy is given out. 2 Particles in Gas are : arranged totally irregularly spread very far apart able to move randomly Particles in Liquids are : closely packed together in an irregular arrangement able to move around past each other Particles in Solids are : packed close together in a regular arrangement or lattice. not able to move freely, but simply vibrate in their fixed positions. In a gas, the intermolecular space is large and can be reduced by increasing the external pressure. Therefore, gases are easily compressible. In liquids, this space is very much smalle r. As a result, liquids are not very compressible. Change in pressure of Gas: pressure increases → volume decreases → gas compressed pressure decreases → volume increases → gas expand Change in temperature of Gas: temperature increase → volume increase → gas expand temperature decrease → volume decrease → gas compressed An increase in temperature increases the kinetic energy of each particle, as the thermal energy is transformed to kinetic energ y, so they move faster and there is less chance of interaction between them. The gas particles move more freely and occupy a greater volume. 3